Offshore oil drilling requires the conveyance of oil from underwater wellheads to shore or other surface installations for further distribution. The resistance to flow of liquid products such as oil increases as temperature decreases. To avoid a substantial decrease in temperature, the pipelines are generally insulated. Furthermore, the underwater environment exposes equipment to compressive forces, near-freezing water temperatures, possible water absorption, salt water corrosion, undersea currents and marine life.
Polyurethanes are often used for insulating such subsea applications due to general ease of processing (two-component molding) and good mechanical properties (strong and tough elastomer). However, such insulation may suffer from hydrolytic degradation when exposed to hot-wet environments. In fields where the oil temperature is high at the wellhead, there is a possibility of degradation of the polymer network if water were to ingress, which would negatively impact the insulation performance of the materials.
Polypropylene is another kind of material also used to insulate such pipelines, however; this requires a difficult application process, which is the extrusion of several layers, and such insulation generally does not possess the attractive mechanical properties of polyurethane.
Another proposed method of insulating undersea systems is the use of pre-cast sections of rigid epoxy-syntactic foam. This material comprises a rigid epoxy resin mixed with a high volumetric proportion of hollow glass or ceramic spheres. Although this material exhibits excellent thermal conductivity, it is very brittle. Due to the rigidity and brittleness of this material, it is easily damaged when subjected to sudden impacts or high stress levels. To compound this problem, rigid epoxy-syntactic foams are difficult to repair. Removal or replacement of this material is extremely difficult because the sections are bonded to the surface using adhesives or mechanical fasteners.
With the continuing focus on offshore drilling, there continues to be a need for improvements in the materials for insulating the pipelines and associated equipment.